1. Field of the Invention
The present invention relates to an image stabilizing apparatus having blur correction means for correcting image blur caused by hand shake or other reasons and to an image pickup apparatus equipped with such an image stabilizing apparatus.
2. Description of the Related Art
In current cameras, many operations, such as the determination of exposure and focusing, that are important in photographing, are automated, and the possibility of failure in photographing with such cameras is low, even if the photographer is not skilled in the handling of cameras. In addition, systems for preventing influences of hand shake on a camera have been developed. Thus, factors that can lead to failure in photographing have been being reduced.
In the following, a system for preventing the influences of shake will be described briefly.
Camera shake caused by hand movement at the time of photographing is typically a vibration of a frequency of 1 to 10 Hz. A basic method of making it possible to obtain a photograph free from image blur even when the aforementioned camera shake occurs at the time of shutter release is to detect the vibration of the camera caused by hand movement and to shift a blur correction lens in accordance with the detected value. Therefore, to make it possible to take a photograph free from image blur even when camera shake occurs, it is necessary first to detect vibration of the camera and secondly to correct changes in the optical axis caused by the camera shake.
The detection of the aforementioned vibration (or camera shake) is made possible, in principle, by equipping the camera with vibration detection means for detecting acceleration, angular acceleration, angular velocity and angular displacement etc., and appropriately processing these detection outputs for the purpose of camera shake correction. In addition, blur correction means for decentering the photographing optical axis based on detected information is driven to reduce image blur.
FIG. 10A is a plan view of a single lens reflex camera, and FIG. 10B is a side view of the same.
The image stabilizing system built in an interchangeable lens 80 mounted on this single lens reflex camera is adapted to perform image blur correction with respect to vertical camera shake and horizontal camera shake that are respectively indicated by arrows 82p and 82y relative to the optical axis 81. On or in a camera body 83 are provided a shutter release member 83a, a mode dial 83b (which also functions as a main switch), a retractable flash 83c and a camera CPU 83d. 
In FIGS. 10A and 10B are also shown an image pickup element 84 and a blur correction mechanism 85 that drives a correction lens 86 in the directions indicated by arrows 85p and 85y in FIGS. 10A and 10B, respectively, to perform image blur correction with respect to the directions indicated by arrows 82p and 82y. The camera is equipped with angular velocity sensors 86p and 86y that detect movement in the directions indicated by arrows 82p and 82y respectively. Arrows 86pa and 86ya respectively indicate the directions in which the angular velocity sensors 86p and 86y are sensitive. The outputs of the angular velocity sensors 86p and 86y are subjected to computation in a lens CPU 87 so as to be converted into blur correction values for the blur correction mechanism 85.
In synchronization with half-depression of the shutter release member 83a provided on the camera body 83 (which operation triggers photometry and focusing in preparation for shooting), the blur correction values are input to coils in the blur correction mechanism 85 through a driver 88. Thus, image blur correction is started.
In the image stabilizing system described in the foregoing with reference to FIGS. 10A and 10B, use is made of the angular velocity sensors 86p, 86y in shake detection. The camera body 83 is subject not only to rotational shake indicated by arrows 82p and 82y but also to translational shake indicated by arrows 11pb and 11yb. However, in common shooting conditions, rotational shake indicated by arrows 82p and 82y is dominant, and image deterioration caused by translational shake indicated by arrows 11pb and 11yb is not significant. Therefore, to detect camera shake, it is sufficient to provide only the angular velocity sensors 86p and 86y. 
However, at very short shooting distances (i.e., in photographing conditions in which the photographing magnification is high), image deterioration caused by translational shake (which will be hereinafter referred to as shift shake) indicated by arrows 11pb and 11yb is not negligible. For instance, in the case of macro shooting in which subjects at distances of as short as around 20 centimeters are shot, or in the case where the focal length of the photographing optical system is very long (e.g., 400 mm) even though the subject distance is around 1 meter, it is necessary to positively detect shift shake to drive the image stabilizing apparatus.
Japanese Patent Application Laid-Open No. H07-225405 discloses a technology in which an acceleration sensor for detecting acceleration is provided to detect shift shake, and an image stabilizing apparatus is driven based on the output of the acceleration sensor in addition to the output of an angular velocity sensor that is provided separately.
In the case where an acceleration sensor is used, it is necessary to make correction with respect to the force of gravity acting thereon. The gravity correction leads to an increase in the amount of computation, and the apparatus is difficult to handle since it is necessary to always stabilize the computation output. For these reasons, this system is not suitable for use in consumer products.